Advanced Game Technology CMPCD3026 CMPSEM044

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Advanced Game TechnologyCMPCD3026-CMPSEM044
Abdennour El Rhalibi Room 723 a.elrhalibi_at_livjm.ac
.uk
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Course Details (Attempt)

• 3D Game Engines Components
• DirectX D3D, 3D Modelling and Rendering
• Meshes, Level Loading and Editing, LOD
• Camera Setting and Animation
• Terrain Rendering
• Spatial Data structure BSP and PVS
• NPC Behaviour and 3D PathFinding A, Flocking,
  Scripting
• 3D Collision Detection
• Game networking Issues Architecture, Protocol,
  Event Synchronisation
• Shading languages
• Introduction to Console Programming

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3D Graphics with Direct3D 9Lecture 2

• Abdennour El Rhalibi

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The Features Of DirectX

• Today's games use DirectX and so support many if
  not all of the graphical features provided by
  this SDK.
• Polygons
• Shading
• Textures
• Lights
• Environmental Effects
• Hardware

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D3D Architecture

• Microsoft Direct3D provides device independence
  through the hardware abstraction layer (HAL)
• HAL is a device-specific interface
• Application doesnt directly access video card

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3D Rendering systems

• The modeling-rendering paradigm
• Graphics pipeline
• At the head of the pipeline, all of a model's
  vertices are declared relative to a local
  coordinate system.
• The first stage of the geometry pipeline
  transforms a model's vertices from their local
  coordinate system to a coordinate system that is
  used by all the objects in a scene.
• In the next stage, the vertices that describe
  your 3-D world are oriented with respect to a
  camera.
• The next stage is the projection transformation.
  In this part of the pipeline, objects are usually
  scaled with relation to their distance from the
  viewer in order to give the illusion of depth to
  a scene.
• In the final part of the pipeline, any vertices
  that will not be visible on the screen are
  removed. This process is called clipping. After
  clipping, the remaining vertices are scaled
  according to the viewport parameters and
  converted into screen coordinates. The resulting
  vertices - seen on the screen when the scene is
  rasterized - exist in screen space.

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Rendering vs. Rasterization

• Many times these words are used interchangeable,
  but there are differences
• Rendering
• generating a pixel-by-pixel image based on the
  objects (primitives, bitmaps, etc.) currently in
  the scene and how they interact
• Rasterization
• the converting of geometric entities (primitives)
  to pixel assignments
• also called scan conversion
• the raster is the array (data structure) of
  picture elements (primitives)
• Bottom-line
• rendering is a higher-order operation that uses
  rasterization

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Summary 20 easy steps ?

• Setup
• Direct3DCreate9()
• GetDeviceCaps()
• GetAdapterCount() and GetAdapterModeCount()
• D3DPRESENT_PARAMETERS
• CreateDevice()
• Resources
• CreateVertexBuffer
• CreateIndexBuffer
• CreateTexture
• CreateVertexShader()
• CreatePixelShader()
• Rendering
• Begin/EndScene()
• SetMaterial(...)
• SetLight(...)
• LightEnable(...)
• SetViewport(...)
• SetTransform(...) - World, view and projection

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Direct3D object

• Direct3D is implemented through Component Object
  Model (COM) objects and interfaces.
• Direct3D object is the first object that your
  application creates and the last object that your
  application releases
• Functions for enumerating and retrieving
  capabilities of a Direct3D device are accessible
  through the Direct3D object. This enables
  applications to select devices without creating
  them
• EXLPDIRECT3D9 g_pD3D NULL
• if( NULL (g_pD3D Direct3DCreate9(D3D_SDK_VER
  SION)))
• return E_FAIL

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D3D Device

• D3D Device is the rendering component of Direct3D
  
• Encapsulates and stores the rendering state
• Performs transformations and lighting operations
  and rasterizes an image to a surface.
• Two types of devices HAL and software (HEL)
• You can think of these devices as two separate
  drivers, one is a software/reference driver and
  the other is the hardware driver
• Can have three different vertex processing modes
  software vertex processing, hardware vertex
  processing, and mixed vertex

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Example Create a D3D Device

• Refer to to Direct3D Tutorial 1
• Step 1. Create a window
• Step 2. Init Direct3D
• Step 3. Handle system messages
• Step 4. Render and display a scene
• Step 5. Shut down and clean up

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Basic Concepts

• DX uses Left Hand Coordinate System. OpenGL uses
  Right Hand Coordinate System
• Primitives are built using vertices, stored in
  vertex buffers
• Different types of primitives D3DPT_POINTLIST,
  D3DPT_LINELIST, D3DPT_LINESTRIP,
  D3DPT_TRIANGLELIST,  D3DPT_TRIANGLESTRIP, D3DPT_T
  RIANGLEFAN
• Each face has a normal associated with it.
  Normals are vectors perpendicular to the faces
  surface and point the way the face is facing
• Face normals are specified using order of
  vertices, Clock-Wise or Counter-Clock-Wise
• Faces with normal facing away from the camera are
  usually backfaced culled

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3D Primitives

• 3-dimensional shapes can be composed of 2D
  (coplanar) primitives in space (usually
  triangles).
• Each triangle (or coplanar polygon) on a 3D shape
  is called a face.
• Smooth surfaces can be achieved by enough
  primitives and correct use of shading.

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Making other shapes using Triangles

• How many vertices, edges, triangles to make a
  cube?
• 8 vertices?
• 18 edges
• 12 triangles

• How about an x-wing fighter?
• 3099 vertices
• 9190 edges
• 6076 triangles

http//gts.sourceforge.net/samples.html
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Graphics Data

• While a scene is being rendered, where should the
  vertex data be stored?
• storing it in system memory (RAM) requires slow
  copying to the video card
• E.g. by simply declaring vertices
• default behavior in Direct3D for vertices
• storing it directly in the graphics card is best
• this is where vertex buffers come in

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Vertex Buffers

• Vertex buffers, represented by the
  IDirect3DVertexBuffer9 interface, are memory
  buffers that contain vertex data
• Vertex buffers can contain any vertex type -
  transformed or untransformed, lit or unlit
• The flexibility of vertex buffers make them ideal
  staging points for reusing transformed geometry
• Ex Rendering models that use multiple textures
  the geometry is transformed only once, and then
  portions of it can be rendered as needed,
  interleaved with the required texture changes
• Vertex buffer is described in terms of its
  capabilities if it can exist only in system
  memory, if it is only used for write operations,
  and the type and number of vertices it can
  contain traits described by D3DVERTEXBUFFER_DESC

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Rendering from VB

• Set the stream source by calling the
  IDirect3DDevice9SetStreamSource method
• d3dDevice-gtSetStreamSource( 0, g_pVB,
  sizeof(CUSTOMVERTEX) )
• Inform Direct3D which vertex shader to use by
  calling the IDirect3DDevice9SetVertexShader or
  IDirect3DDevice9SetFVF method
• d3dDevice-gtSetFVF( D3DFVF_CUSTOMVERTEX )
• After setting the stream source and vertex
  shader, any draw methods will use the vertex
  buffer
• d3dDevice-gtDrawPrimitive( D3DPT_TRIANGLELIST, 0,
  1 )

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Dealing w/ Vertex Buffer

• Creating Vertex Buffer
• //g_pVB is a variable of type LPDIRECT3DVERTEXBUFF
  ER9
• if( FAILED( d3dDevice-gtCreateVertexBuffer(
  3sizeof(CUSTOMVERTEX), 0 / Usage /,
  D3DFVF_CUSTOMVERTEX, D3DPOOL_DEFAULT,
  g_pVB ) ) )
• return E_FAIL
• Accessing Vertex Buffer. Need to lock because VB
  can be in device memory
• // Lock the buffer to gain access to the vertices
  
• VOID pVertices
• if(FAILED(g_pVB-gtLock(0, sizeof(g_Vertices),
  (BYTE)pVertices, 0 ) ) )
• return E_FAIL
• memcpy(pVertices, g_Vertices, sizeof(g_Vertices))
  
• g_pVB-gtUnlock()
• Make sure your application properly accesses the
  allocated memory. Otherwise, you risk rendering
  that memory invalid.

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Making a simple cube in Direct3D

• For a cube, well need 12 triangles
• we could declare construct 36 vertices, each
  with its own coordinates
• well see a more efficient means using only 8
  vertices
• load into vertex buffer
• at draw time, provide vertex buffer as triangle
  list

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Index Buffers

• Constructing 36 vertices to create a cube using
  triangles!!
• inefficient use of memory
• a real cube only has 8 vertices (one for each
  cube corner)
• In a large-scale application, redundant data is
  costly
• Index buffers are a mechanism for sharing vertex
  data among primitives
• a buffer that stores indices into vertex data
• What does that mean?
• an array (or vector, etc.) that describes shapes
  (e.g., triangles) using indices of constructed
  vertices in vertex buffer
• groups of 3 indices describe one triangle

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Example, create the index buffer

• vertices of a unit cube
• // vertices of a unit cube
• vertices0 Vertex(-1.0f, -1.0f, -1.0f)
• vertices1 Vertex(-1.0f, 1.0f, -1.0f)
• vertices2 Vertex( 1.0f, 1.0f, -1.0f)
• vertices3 Vertex( 1.0f, -1.0f, -1.0f)
• vertices4 Vertex(-1.0f, -1.0f, 1.0f)
• vertices5 Vertex(-1.0f, 1.0f, 1.0f)
• vertices6 Vertex( 1.0f, 1.0f, 1.0f)
• vertices7 Vertex( 1.0f, -1.0f, 1.0f)

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A Cube Index Buffer Solution

• // define the triangles of the cube
• // front side
• indices0 0 indices1 1 indices2
  2
• indices3 0 indices4 2 indices5
  3
• // back side
• indices6 4 indices7 6 indices8
  5
• indices9 4 indices10 7 indices11
  6
• // left side
• indices12 4 indices13 5 indices14
  1
• indices15 4 indices16 1 indices17
  0
• // right side
• indices18 3 indices19 2 indices20
  6
• indices21 3 indices22 6 indices23
  7
• // top
• indices24 1 indices25 5 indices26
  6

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Advantages Disadvantages of Index Buffers

• What are the advantages?
• more efficient memory management
• What are the disadvantages?
• vertices have to share color data
• vertices have to share normal data
• may result in lighting errors

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How about the same cube multiple times?

• We can construct a single vertex buffer
• Set the world transform for the first cube
• Draw the first cube using our vertex buffer
• Set the world transform for the next cube
• Draw the next cube using our vertex buffer

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Additional Primitives

• Point List

• Line List

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Additional Primitives (2)

• LineStrips

• Line List
• vs
• Line Strip

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Additional Primitives (3)

• Triangle List

• Triangle Strips

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Additional Primitives (4)

• Triangle Fan

• Teapot

http//www.codesampler.com/d3dbook/chapter_05/chap
ter_05.htm
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D3D Primitives

• D3DPT_POINTLIST, D3DPT_LINELIST, D3DPT_LINESTRIP,
  D3DPT_TRIANGLELIST,  D3DPT_TRIANGLESTRIP, D3DPT_T
  RIANGLEFAN

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Example Rendering Vertices

• Refer to to Direct3D Tutorial 2
• Step 1. Setup vertex buffer (in C also define
  custom vertex type)
• Step 2. Render

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Conclusion

• We have quickly overviewed some basic techniques
  for 3D graphics in any system.
• Use the Direct3D tutorials and documentation to
  familiarize yourself with the APIs.